The present invention relates to the ventilation of electrical devices in an avionics bay.
The avionics bay of an aircraft, more commonly referred to as an E/E bay, is arranged in a compartment situated under the floor structure of the flight deck, between the nose of the aircraft and the cargo compartment.
Here, most of the aircraft electrical and/or electronic equipment is grouped together in racks. A rack, in the known way, comprises a framework made up of vertical uprights joined together by horizontal transverse shelves, to form a plurality of housings. The electrical and/or electronic equipment of the aircraft is introduced into these housings in the form of functional units. The face of the rack via which the units can be introduced will be referred to in the rest of the description as the open face.
During operation, the electrical equipment in the avionics bay dissipates heat and requires continuous cooling. For this purpose, ventilation circuits based on a principle of blowing and extracting air are installed in the avionics bay. Some elements that make up the ventilation circuits are bulky because they pass round the racks and are complicated to fix in the avionics bay.
FIG. 1 illustrates the circuit used for ventilating a set of racks 1 in an avionics bay of an aircraft. A set of racks is defined as a row of a plurality of racks 3 positioned side by side. The respective frameworks of each of the racks 3 are then fixed together, to form a framework that is common to the set of racks 1.
The ventilation circuit for a set of racks 1 comprises two independent circuits: an air blowing circuit C1 and an air extraction circuit C2. These two circuits C1, C2 are connected to a plurality of air transmission pipes 5 of the set of racks 1. More specifically, each rack 3 comprises at least one air transmission pipe 5 which passes through it from top to bottom in order to cover the largest possible surface area for exchange of heat with the electrical/electronic equipment housed in the rack 3. Each air transmission pipe 5 has a first end 6 situated at the top of the rack, near the top of the avionics bay, and a second end 7 situated at the bottom of the rack, near the floor for walking on of the avionics bay.
The path followed by the flows of air through the various elements illustrated in FIG. 1 is embodied by arrows.
The blowing circuit C1 is made up of main inlet trunking K1 for blowing cold air (arrow Fa) into each rack 3 of the set of racks, which trunking is coupled to a plurality of air inlet pipes E1. Each air inlet pipe E1 is connected to a first end 6 of an air transmission pipe 5.
The cold air becomes heated up as it passes along an air transmission pipe 5. The hot air (arrow Fc), leaving each air transmission pipe 5, is discharged by the air extraction circuit C2 which comprises a plurality of air extraction pipes E2. Each air extraction pipe E2 is connected to a second end 7 of an air transmission pipe. The air extraction pipes E2 are coupled to main hot air extraction trunking K2 which, connected to suction means (not depicted in the figure), is able to suck up the hot airflows. The sucked-up hot air is then discharged (arrow Fd) from the aircraft or treated (arrow Fd) on board the aircraft.
In FIG. 1, and for the sake of making the figure less cluttered, the extraction trunking K2 is depicted in the bottom part of the avionics bay. In real life, the main trunking K1 and K2 are generally situated in the upper part of the avionics bay. The air extraction circuit C2 therefore occupies a great deal of space because the air extraction pipes E2 continue over most of the height (axis z) of the avionics bay.
As a result, the volume occupied by the air extraction circuit C2 presents a great many problems in designing aircraft, especially since, in aircraft of more recent design, the size and number of sets of racks is constantly increasing. However, the size of the avionics bay has to be contained given the constraints on the availability of space within an aircraft.
Thus, installing an air extraction circuit C2 is a complex and costly matter because it entails the production of a great many components of different types and shapes so as to free up as much space as possible in the avionics bay. Some of these components are delicate and the technicians moving around in the avionics bay have therefore to take a great many precautions when performing maintenance operations in the avionics bay. Further, an air extraction circuit C2 comprises multiple complex and heavy systems, such as air suction fans or various valves for example. The weight of these systems means that they have to be fixed to the structure of the aircraft and that additional support elements have therefore to be provided, all of this undermining the very desirable search to find ways of reducing size and bulk in aircraft.